Another thing about M. Clarke is that he's an excellent fielder.
But i think clarke's place is pretty much interchangable with whomever the selectors want to play. If they put in a bowler (eg tait, johnson, macgill for a 2nd leggie etc) then our bowlers can still bat quite a bit (lee, to an extent: warne, S. clark) and our batsmen look in fine form. If they want to play a batsman like clarke, our bowling attack still looks pretty solid with lee, mcgrath, clark, warne and...hussey and clarke rolling over the wrist for a few overs. Or they can play an all rounder like watson (he's underachieved IMHO and needs more time).